This invention relates to tools used in sanding, abrading or polishing of surfaces. More specifically, the invention relates to hand tools on which a sheet of polishing or abrading material can be mounted.
A common use for such a sanding, abrading or polishing hand tool is in the finishing of wood products. For purposes of brevity, herein the term "finishing" shall be understood generally to encompass all forms of sanding, abrading, polishing, buffing and like activities, and the invention described and claimed herein is referred to as a finishing tool. At the same time, use of the term finishing is not intended as a limitation on types of activities or uses to which the invention can be put.
Perhaps the most important step in creating a handcrafted wood product is the finishing step. Hand tools exist to hold sheeted finishing materials in place so that they may be used to give a surface, such as wood, a particular kind of texture. Such sheeted finishing materials include sandpaper, emery paper, polishing or rubbing cloth, or any desired sheeted finishing material to be rubbed against a surface as the block is operated.
With the advent of diverse, high quality abrasives, sanding has become a particularly important process both for shaping surfaces and preparing them for finishing. Many power tools have evolved to facilitate this process, but hand sanding remains an indispensable component of most finishing jobs. Indeed, it has long been known that a sanding block greatly increases the efficiency of hand sanding by fully and evenly utilizing the sandpaper supported on the surface of the sanding block. A sanding block also facilitates hand sanding by providing a comfortable and convenient handle or grip with which to manipulate the sandpaper attached to the block.
The principal elements of an effective finishing tool for use as a sanding block are:
(1) a surface that will support sandpaper and uniformly apply it to the work surface; PA1 (2) a means for attaching the sandpaper to the support surface securely, efficiently, inexpensively, safely and conveniently, so the sandpaper can be easily removed and replaced when desired; and PA1 (3) a handle which allows comfortable and convenient manipulation of the tool.
Thence, in one respect a finishing tool must be capable of firmly and tautly holding sheeted finishing material against the support surface of the tool so that the sheeted finishing material does not move or break free when the finishing tool is subjected to the forces and repetitive motions of sanding. Inadequately held sheeted finishing material can break or tear, resulting in uneven and less effective finishing, wasted time and increased costs.
In another respect, somewhat inconsistent with the objective of firmly attaching the sheeted finishing material to the finishing tool, the sheeted finishing material should be easily removable from the tool to substitute fresh or different sheeted finishing material. Sheeted material can lose effectiveness when it becomes clogged with debris, worn down or torn as it is used. In addition, sometimes during the finishing process it is desirable to change grades or kinds of sheeted finishing material. Not only must sheeted finishing material be easily removed, but the new sheeted finishing material must also be placed into a firm and taut position on the tool with a minimum of effort.
Three basic concepts have been long employed in sanding blocks. The first concept is that of wrapping a piece of sandpaper around a rectilinear block and holding it tight against the block with pressure from your hand. The second concept is to employ a block on which a strip of sandpaper is wrapped upwardly around the ends and impaled on pins or nails sticking upwardly out of the block, the nails in turn being covered either by a rubber flap which must be bent back to expose the pins or by a plastic casing which snaps over the entire top of the block. The third concept is that of using a mild adhesive to glue sandpaper to the bottom of the sanding block so that it can be peeled off and replaced when it is worn out.
All of the three types of commercially available sanding blocks have their drawbacks. The rectilinear block is the simplest and it can be effective in the hands of an experienced craftsman, but it does require a high degree of skill, coordination and strength to keep the assembly together. Even in the hands of a skilled operator it is fatiguing to use, as a constant firm grip is required.
The blocks that use pins to secure the sandpaper have the drawback that the paper can never be pulled tight across the surface of the block. There is always a little bit of play in the paper when it is mounted. This allows the sandpaper to work back and forth while the block is being used, causing the paper to wear out faster and wasting energy in the process.
Also the pins can prick the operator while removing and replacing the paper. The rubber flaps used on such blocks are also problems in that they are prone to break from bending back to expose the pins. The rubber flaps are also difficult to hold back when installing.
Blocks employing adhesives to secure the paper have their problems too. First, only specialized expensive paper can be used. Second, the required paper is not as widely available as conventional sandpaper. Third, the adhesive surfaces tend to load up with sanding dust causing the adhesive quality to deteriorate.
Attempts have been made to improve on the foregoing concepts but none have been entirely successful. For example, sanding blocks that permit easy and convenient changing of sand paper tend not to hold the sandpaper securely and tautly; while sanding blocks that securely and tautly hold sand paper tend not to permit easy and convenient changing of the sandpaper.
One prior art finishing tool is seen in F. Schuch, Fine Woodworking Magazine, July/August, 1987, pp 11-12. Schuch proposes a solid slab of wood with shallow "v-groove" notches along the lengths of opposite edges. A length of wood doweling can fit into each v-groove to clamp the edges of a piece of sandpaper into respective v-grooves. Both ends of each wood dowel extend beyond the width of the wood slab. Strips of inner tube connect the extending ends of opposing dowels to keep the dowels clamped against the sandpaper in the v-grooves. However, if held by hand and reciprocated, the wood doweling is likely to be dislodged from the v-grooves as a result of direct hand contact with the dowels or the external rubber strips.
Another prior art finishing tool is proposed by Fisk, U.S. Pat. No. 1,183,444. Fisk uses spring-driven clamping mechanisms imbedded in a base to secure sandpaper ends. Since each clamping mechanism is located on the top surface of the sanding base, gripping and putting pressure on the device during use could engage the spring, thereby loosening the sandpaper. Further, being embedded in the base, the clamping mechanism is not optimally located for efficient insertion and removal of sanding paper.
Forsblade U.S. Pat. No. 2,189,980 proposes a hinged assembly of two blocks, the adjacent faces of which are forced apart on one side of the hinge by a wedge while the same faces come together on the other side of the hinge in a pinching motion. This allows for the mounting of sheet abrasive on both outside faces of the hinged blocks, but it is not adapted in any way to provide a comfortable grip or handle. The Forsblade device is also an unnecessarily complicated and expensive product to build. Further, the wedge is subject to dislocation and loss.
Nordlund U.S. Pat. No. 2,220,727 proposes a tool employing a wedge to draw two blocks tightly together. This tool provides a comfortable grip, but the wedge is subject to easy displacement during use. The three parts can become separated and lost, and the open edge of the sandpaper is exposed to the forward and backward motion of the block. This allows dust and debris to get between the paper and the block, spoiling the uniformity of the finish and causing the paper to break down, tear and fold.
In addition to having structural and functional disadvantages many prior art finishing tools are unduly expensive or difficult to manufacture. An example of such tools are the aforementioned tool proposed by Nordlund and the tool proposed by Minnick et al, U.S. Pat. No. 2,402,009, which has elaborate hinges and structure.
Therefore, it can be seen that there is a need for a finishing tool which provides improved attachment and removal of sheeted finishing material, handling and finishing results.